Joseph John Thomson

Discoverer of the Electron

Joseph John Thomson

Discoverer of the Electron

JJ Thomson Growing Up

Joseph John Thomson was born December 18, 1856. His father wanted him to get an engineering career, but since no engineering apprenticeship could be found he was temporarily sent to a college in Manchester at the age of 14. Thomson won a scholarship in 1876 and entered Trinity College, Cambridge. This is where he studied and worked for the rest of his life. Thomson was both respected and well liked. Students came from all around the world to study with him.

What is a cathode ray?

A cathode ray (aka Electron beam or e-beam) is just a stream of electrons. Scientists were able to observe the effects of cathode rays before the discovery of the electron. The cathode ray tube is a glass tube under vacuum, that has an electrode (two charged poles) at either end. When turned on, the glass on the positive end is observed to be glowing.

JJ Thomson's Cathode Ray Studies

Thomson's study of cathode rays began in 1894. In 1895 he proved that they carry a negative charge. In 1897 he showed that the rays are deflected in both magnetic and electric fields when being passed through a vacuum. His identification of the electron called for a revision of the atomic concept. He visualized it as a mass of positively charged matter in which electrons were distributed accordingly.